Double hell if your garages faces south or west, even if the door is insulated (most homes down here are not). 

No matter how much new build there is, location will always insulate the older properties;  and fully rehabbed older properties are in fierce demand right now.  

The duplex has great insulated walls so we can't hear anything from the other side.

That is often the case when you have a bad PM insulate between the owner and the property, so they don't really see (or care) what's going on.Milwaukee has been re-inventing itself over the last 10 years or so and that is gaining momentum.

A regular partition wall with insulation is not going to cut it for noise sensitive residents.

They have only seen one - and it came a day after I was in the attic fixing insulation that an electrician removed to re-wire the upstairs.

More insulation in the roof.  

To offer asset protection and liability insulation, think about establishing a limited liability corporation (LLC) or other legal structures.

If the garage is not built to support the weight of additional floors or is not adequately reinforced, it may not be suitable for conversion.Insulation: Another important consideration is insulation.

ADU has to have a door leading to the interior main dwelling, effectively making the unit extremely less private and less insulated.